Travel through the Taxing Cellar to reach the Ultimate Altar of Earth. Once you worship there, you get +50 MaxHP and intrinsic regeneration--while under your max HP, you gain 1HP automatically every 4AP you spend (this does stack with the healing spells). The reward message also encourages you to earn glories through "aggregation":

You worship at the altar and gain Mastery of Earth! +50 MaxHP, intrinsic regeneration.
You may also now gain glory by aggregation!

Note that unlike the Vents, free access to the cellar is not granted once the altar is worshiped at.

I have just completed the Ultimate Altar Of Earth and was able to move around freely with no items being taken, although I may not have had them to take. It may be best to bag everything you want to keep before trying this out further. Anoki 23:08, 12 February 2009 (GMT)

I completed it a few months ago, and if nothing has changed, then completing the quest allows you to walk around freely, but with a catch. If you have the item required to pass, you will lose it. If you do not have the item, however, you can move without losing anything. I'm not sure if it is intended to work this way, but unless something has been changed, that is how it works. --JAD 19:19, 13 February 2009 (GMT)